Different network operators which provide voice and data services to their own subscribers may also provide such services to subscribers from other networks. These different networks may be available in a same country. When a subscriber leaves his home network and receives service from another network, he is said to be roaming. More precisely, “national roaming” or “home roaming” is where customers roam from their home network to other networks within the same country. This type of roaming is required when the home network does not provide service in all of the nation's territories and/or states). Another case of roaming referred as “international roaming” when the network operator provides services in a foreign country, International roaming involves making or receiving calls or sms . . . from outside the home country's borders.
In order to offer roaming services to their Subscribers when traveling, the Mobile Network Operators (MNO) or Mobile Virtual Network Operators (MVNO) need to put in place Roaming agreements with each operator in each country. Roaming Hubs give access to the MNO or MVNO to their hundreds of roaming agreements and to their infrastructure. A subscriber can then roam to networks with which the operator of the subscriber's home network has a roaming agreement. When a subscriber roams in a foreign network, he may roam onto one of the plurality of communication networks which are available within the relevant geographical area and have a roaming agreement with the home network.
Roaming behavior is for example defined in telecom standards and is controlled for example by data stored on the subscriber identity module (SIM) card, in suitable files present on the SIM such as EFLOCI file, EFPLMNSel, EFFPLMN, etc.
As well known, the EFLOCI contains the last selected network. More precisely, this file contains information about the mobile network the user is connected to at all times, and contains the Registered Public Land Mobile Network (RPLMN) which is the current roaming network the mobile is registered to. The EFLOCI file comprises the Location Area Information (LAI) which comprises the Mobile Country Code (MCC), the Mobile Network Code (MNC), the Location Area Code (LAC). The MCC identifies the country to which the network the user is connected to belong to. This file may be modified each time the user connects to a different network. The MNC is a code which identifies a network within a country. Then the MNC of the EFLOCI in combination with the MCC, defines the mobile network the user is connected to. The LAC identifies the location area where the subscriber is operative.
The file EFPLMNSel indicates for example the user's preferred network (PLMN) or operator to which the terminal must try to connect to when the user cannot connect to his home network, i.e. when the user starts roaming. If the terminal can not connect to the network indicated in the EFLOCI, it then will try to connect to one of the preferred network as indicated in the EFPLMNSel, otherwise, it will try to connect to any of the available network.
The EFFPLMN file contains the forbidden list of networks which should not be selected. As per GSM standards, when a handset or a mobile station (MS) tries to latch on to any network, and if the network (MNO) does not provide access, the MS updates the EFFPLMN on SIM Card with specific MCC-MNC of that network. This file is further used by MS to identify those networks which are Forbidden PLMN. The elementary file contains coding for four Forbidden PLMNs (FPLMN). It is read by the handset as part of the SIM initialization procedure and indicates which PLMNs which the MS shall not automatically attempt to access.
The handset modifies its roaming behavior based on the contents of such roaming control files on the SIM card. For doing so, the user needs to be successfully registered with the mobile service of the foreign network, also called here visited network.
Dual IMSI is for example a known SIM-based standalone application which manages two IMSIs for a subscriber in one SIM card: one IMSI for the Home network (MNO) and one IMSI for the international roaming. The home IMSI is used in the subscriber's home country. The Roaming IMSI is used when abroad for connection to a roaming hub. Switching between the two IMSIs is handled automatically by the application, depending on location. The application detects when the end-user is roaming and switches to the Roaming IMSI.
All MNOs which use Dual IMSI application on SIM card, one for Home network and another for Roaming network ensure that while using the Home IMSI, the user does not get service in Roaming or International Network. Similarly, it is also ensured by MNO that while using the Roaming IMSI, the user does not get service in Home network.
As a managed service, this Dual IMSI is extremely simple to implement. The application is deployed over-the-air, so the start up is rapid, and any subsequent changes to country lists are made in the same way.
Nevertheless, currently in many countries, such an automatic application may not be available and if it is available it may be then too expensive for the MNO to deploy. In this case, it may be necessary for the end-user to manually change the IMSI from Home IMSI to Roaming IMSI when roaming in foreign country, and similarly change the IMSI manually from Roam IMSI to Home IMSI when the end-user returns back in his home network. This can be done for example by using a SIM Tool Kit application. Furthermore, as previously described, the switch from the Home IMSI to the Roaming IMSI, and vice versa is only possible if the Home network has established an agreement with the visited network. Operators need to develop new bilateral agreements with selected partners, still using hub-based services for other destinations, which may be costly and long to put in place.
The switch can only be possible if the foreign country has been identified. Thus if the application has some problem to identify the new roaming location, the switch will not occur and the end-user will not be able to use his mobile.